Jesus Perez believes the FA Cup is a good opportunity for Saints to challenge for silverware this season.
But he also insisted the club will assess the fitness of their first team regulars before throwing them into action at Sunderland.
With Saints in good form and entrenched in upper mid-table, many fans are hoping they will prioritise an FA Cup run this season.
They have already won through to a fifth round tie at the Stadium of Light and many of the Premier League big guns are set to have exited the competition by the quarter-final stages.
Mauricio Pochettino admitted on Monday it would be very hard to name the same side during this run of three games in a week on heavy pitches, even if all his players were technically fit.
He also said he expected the full squad would be used.
There was just one change to the starting line-up for the game against Hull, suggesting Saints may make several more changes for tomorrow’s match.
Perez, assistant manager to Pochettino, said: “We did some changes from Stoke. Our squad is not massive now so the names around are always the same.
“We have to decide some decisions but we need to train and especially analyse from a physical point of view how they are recovering because some of the players are doing very well from a physical point of view but sometimes you need the extra day to fully recover.
“Always we always say the same after a game. We need a couple of days to assess the team.
“We played two games in the last four days, very tough games, also with the conditions and the weather as well.
"We will see how the players are recovering and who is available to play on Saturday.
“It is a game to win to stay in the next round, so obviously we will pick the best team to win.
“Always we did the same, but before Christmas, for example, you have a lot of games and have to rotate the players and use others.”
The only players definitely ruled out are centre half Dejan Lovren and midfielder Gaston Ramirez.
Perez, left, is hopeful they could both recover from ankle injuries they picked up against Sunderland in the league meeting between the sides last month in time for next weekend’s trip to West Ham.
He allayed fears over the fitness of Jose Fonte who posted a picture of himself on a social networking site with three nasty gashes on his leg.
Tomorrow’s match is the fourth time the teams have met this season with two draws in the league and a defeat for a much-changed Saints side in the Capital One Cup.
Perez insists the FA Cup represents a chance of success that Saints will be taking seriously.
“It is going to be an exciting game, an exciting opportunity to get into the next round,” said Perez. “The FA Cup is one of the traditional competitions around the world.
“For this situation, you are playing on a Saturday. If you watch a Spanish cup game, it is played 10pm, there are no kids at the stadium, the stadium is empty.
“It is a traditional competition and one you have to face with full focus.
“It is a good opportunity with how the draw is, some of the good teams are going to be out.
“Hopefully we will get the opportunity to play in the next round."